Not Even the Pentagon Bomb Squad Knows How Fast Insurgent IEDs Degrade

Like all wars, the war in Afghanistan must someday end. But the end of its signature weapon may not arrive on the same schedule.

Insurgents’ homemade bombs, known as improvised explosive devices, look increasingly like a lasting fixture on the early-21st century battlefield. The Pentagon’s bomb squad warns that the cheap, easily fabricated family of explosives are spreading all around the world. But it doesn’t know how long the devices themselves last.

The Joint Improvised Explosive Device Defeat Organization, JIEDDO, collects sheafs of data about the bombs. It knows what sorts of materials go into the bombs, where the materials come from, what countermeasures succeed at stopping the blasts (and which ones fail), and how many of them turn out to be duds. But to date, it hasn’t acquired any data about the lifespan of an improvised explosive device. “There are no historical records or analysis documenting how effective emplaced and undetonated IEDs may become over time,” David Small, JIEDDO’s spokesman, tells Danger Room.

That means the U.S. is largely blind to how long an explosive device nestled in an Afghan culvert will remain a threat to civilians even after the hypothetical day when insurgents close their bomb factories. (After all, those factories don’t stamp a date of manufacture on their deadly weapons.) The fact is IEDs are constructed to kill people with minimal technological sophistication. They’re not constructed to be durable. But the science associated with the materials used in the bombs indicates that they’re likely to remain lethal for a year or more after they’re assembled.

Start with the kind of bang used in the bomb. In Iraq, the devices were often artillery shells or other military-grade hardware daisy-chained together, resulting in a patient, long-lasting bomb. Same for those that used plastic explosives, explains Augustus Way Fountain III, the Army’s senior research scientist for chemistry. “As long as they’re encased and don’t have access to extreme heat,” Fountain says, the bombs are “very, very stable, [lasting] years.”

But those types of devices aren’t often seen in Afghanistan. There, the vast majority of bombs JIEDDO has discovered — some 97 percent — rely on homemade explosives for their explosive force. Sixty percent of that homemade explosive comes from ammonium nitrate derived from Pakistani fertilizer; much of the rest uses potassium chlorate. Ammonium nitrate will degrade based on environmental factors — most importantly, water in the air.

When humidity reaches 55 percent, ammonium nitrate will start absorbing moisture, starting a chemical degradation process. At 15 percent saturation, JIEDDO estimates, the ammonium nitrate probably won’t detonate; at 20 percent, it definitely won’t. “It just gets mushy, harder to work with,” says Jimmie Oxley, a professor of chemistry who focuses on explosives at the University of Rhode Island. (Potassium chlorate, not so much.)

Insurgents, however, have ways of mitigating that. Often the ammonium nitrate or potassium chlorate will be stored in plastic palm-oil jugs, which keeps the moisture out. In the jugs, “they’re pretty much impervious” to the elements, Fountain says. Even without them, the climate in which they’re produced tends not to break down the dangerous compounds. “In the dry, arid environment they’re manufactured in,” he continues, “they can last for a long time.”

Oxley notes that in lab conditions, ammonium nitrate is good for something like a decade. In the real world, “when you look at what [information] the suppliers of ammonium nitrate provide, they usually put a two-year shelf life on their products,” she says. Putting the explosive in plastic jugs, burying it in dry soil — all of that acts as a preservation agent for the bombs. “It’s safe to say they can last a year or two,” Oxley judges, and potassium chlorate-based bombs, which lack the same sensitivity to moisture, are probably good for longer.

At the same time, just because a bomb is capable of detonating doesn’t mean it will. And lots of things impact whether a bomb detonates (and degrades) besides the explosive used: its construction, its wiring, its detonation mechanisms. As befitting a bomb that costs, on average, $265 to construct, most improvised explosive devices fail. Between April 2011 and April 2012, they saw a 25 percent drop in effectiveness. And they get spotted: according to JIEDDO’s most recent data, U.S. troops encountered over 3,000 IEDs during the final three months of 2012, and safely cleared 69 percent of those they encountered in vehicles and 86 percent of those they encountered on foot.

At least some that failure rate can be attributed to the U.S.’ array of sensors and intelligence methods. But that’s about to drop off, as U.S. troops come home. Lt. Gen. James L. Terry, the day-to-day commander of the war, told Pentagon reporters on Wednesday he was concerned about Afghan troops’ relatively immature counter-IED technology.

But even if insurgent bombs grow more sophisticated, numerous and effective, they’re nothing like the danger from landmines. For one thing, the point of tiny military-grade landmines is to litter a swath of territory to deny it to an adversary. IEDs are usually placed along a road that an adversary travels, and not in great concentrations. For another, the casing and detonation devices of the mines are usually more reliable — and built to resist degradation. In 2011, according to the most recent report from the International Campaign to Ban Landmines, the mines killed or wounded 4,286 people in six countries in 2011.

“I’ve disassembled mines in the Falklands islands, a very harsh climate,” says Colin King, a former British Army bomb-disposal officer, “and the last ones I did were more than 30 years [older] than the event, and some of those were in perfect condition 30 years on. I’ve seen some in Cambodia and in Jordan, particularly in Cambodia where you’ve got a wet climate and poor quality mines, which were nonfunctional very, very quickly. But there are very few IEDs that are going to last for years.”

Science and experience indicates as much. But the data, alas, is lacking. “There are anecdotal reports of IEDs being emplaced underneath roads, paved over and then detonated a long time after, but this is neither reported frequently nor trending to warrant consistent tracking,” JIEDDO’s Small says. “The bottom line: There is no exact answer to degradation.”